The present invention is related to a charger for an industrial truck which has an asynchronous machine and a three-phase AC control unit for converting a battery voltage for the asynchronous machine.
From EP 1 350 664 A2 an industrial truck with charging function is known in which no separate charger for recharging the battery is provided, but an electronic control device controls the charging function, too. For this, a separate voltage transformer with an AC/DC transformer is provided, which converts the mains voltage to the low voltage of the battery, the AC/DC transformer corresponding to a complete charger without a printed circuit board for control in doing so.
From EP 0 849 112 A1 a three-phase AC drive arrangement is known, with a battery-supplied, rotation speed variable three-phase machine and a controlled pulse width modulation inverter for the generation of three-phase current AC voltages for the three-phase machine. Further, a charging device for the drive battery is provided, which is supplied by a three-phase current mains and charges the drive battery. This arrangement requires a lavishly designed motor.
From EP 0 593 472 B1, an on-board charger is known, in which two bridge branches of a power inverter are controlled as upward setting controllers in order to apply a DC voltage to a capacitor, and the further bridge branch of the power inverter is controlled as a downward setting controller in order to create a charging current for the traction battery from the capacitor. This device requires a lavishly designed contactor group.
The present invention is based on the objective to provide a charger for the traction battery of an industrial truck which makes it possible to charge the traction battery with simple means.